Gallica is the digital library of the Bibliothèque Nationale de France (BnF) and is one of the best freely accessible digital archives online, crammed full of brilliant historical sources. It’s fairly easy to navigate, and you can register to save documents and books to your digital workspace.
I’ve personally been using it a lot lately to access all the 19th-century editions of my medieval primary sources from the comfort of my bed, instead of having to trot all the way out to the Bodleian Upper Reading Room!
Scrawling Spires 